Electric projector lamp



D- K. WRIGHT ELECTRIC PROJECTOR LAIP April 22, 1941.

Filed Dec. 1, 1944 3 Sheets-Sheet 1 DANIEL K. WRIGHT:

INVENTOR HIS ATTORNEY April 22, 1947. K wRlGHT 2,419,432

ELECTRIC PROJECTOR LAN? Filed Dec. 1. 1944 I5 Sheets-Sheet 2 7 INVENTOR,

8W, HIS ATTORNEY D. K. WRIGHT April 22, 1947.

ELECTRIC PROJECTOR LAMP Filed Dec.

DANIEL KwRlGHT'.

INVENTOR,

HIS ATTORNEY Patented Apr. 22, 1947 2,419,432 ELECTRIC PROJECTOR LAMP Daniel K. Wright, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation 01' New York Application December 1, 1944, Serial No. 566,193

1 Claim. 1

This invention relates to electric lamps of a general type such as disclosed in my Patents Nos. 2,148,314 and 2,148,315, granted February 21, 1939, and 2,324,972, granted July 20, 1943, which are commonly known as the Sealed Beam type, and are widely used as automobile headlamps. This type of lamp comprises a bulb or envelope composed of sections hermetically sealed together at their edges, one a rear section which generally serves as a reflector, and the other a front cover or lens section. As shown in said patents, the sections are of vitreous material pressed or molded to shape and afterward united at the edges by fusion, and the sections are concave toward one another. The rear section may have a concave light-concentrating surface, preferably paraboloidal when a straight, uniform light beam is desired, with the electric translation means or light source located or centered at its focus. The front cover section may be plain, depolished or matte, frosted, pebbled, fluted, or prismed to transmit and distribute the light or radiation as desired. The initial separateness of the sections facilitates shaping their internal surfaces by pressing exactly as desired, and also facilitates internally coating the rear section (only) with a metallic mirror of silver, aluminum, or other suitable metal(s). These parts may be of lowexpansion glass such as the borosilicate glass disclosed in U. S. Patent No. 1,304,623 to Sullivan et al.

It has heretofore been sought to provide lamps such as above described with light-polarizing front cover glasses. This is especially desirable for automobile headlight lamps, as a means of abolishing the danger and annoyance of blinding glare from the undimmed bright lights of an approaching car at night: i. e., a driver with polarized headlights and similarly polarized glasses would see the road brightly lighted ahead of him by his own lights, but would get neither direct nor road-reflected glare from the polarized headlights of a car coming in the opposite direction. But it has been found difficult and expensive to apply light-polarizing material to the externally convex or crowned covers of such headlamps; and it has proved impracticable to make flat-front lamps (i. e., lamps with flat front sections) to which commercially available sheet or laminated polarizing material could readily be applied, because the envelopes of lamps made with such flat fronts have tended to crack after their component sections have been sealed together, resulting in prohibitively high losses in production.

I have found that by certain modifications of structure and of sealing technique which I have devised, flat-front Sealed Beam type lamps can be produced without serious risk that their composite envelopes will crack as heretofore, and light-polarizing lamps of this character can likewise be produced very easily and economically. The invention also allows of making fiat-front Sealed Beam typ lamps-that are useful in cases where light polarization is unnecessary, Two specific ways of sealing flat front cover sections to rear sections for the purposes of the invention are hereinafter described, and have in common the novel feature that the sealing heat is largely kept away from the flat part of the cover.

Various other features and advantages of the invention will appear from the description of species and forms of embodiment, and from the drawings.

In the drawings, Fig. 1 is a plan view of a flatfront light-polarizing lamp constructed according to the invention, the lamp envelope being shown partly broken away and in section at several places, and its component-. s ections being represented as sealed together only part way around their peripheries; and Figs. 2 and 3 are front and rear views of the component rear and front lass sections by themselves, prior to sealing together, part of the front section being broken away and omitted from Fig. 3.

Figs. 4 and 5 are fragmentary views generally similar to Fig. 1 illustrating other ways of applying a light-polarizer to a flat-front lamp.

Figs. 6 and 7 are tilted front and rear views of rear and front lamp sections, illustrating a modification; and Fig, 8 isa fragmentary sectional view illustrating the forming of a joint between these sections when they are'fused and sealed together.

A sealed beam lamp bulb or envelope 1 is shown in Figs. 1, 2, and 3 as comprising a rear preformed pressed glass concave reflector section 2 internally surfaced with a reflective metallic coating 3, and resembling the reflector section shown in my Patent No. 2,324,972. It has a widened periphery or rim 4 that has a sealing zone 5 for sealing to the front section 6, also preformed of pressed glass: This front lens or cover section 6 differs from that of said patent in-being dish-shaped and having a radiationtransrnitting portion that is substantially flat or planar instead of concave, with a lateral flange or circumferential wall 1 extending to the reflector rim 4 for sealing thereto, and peripherally widened into a rim 8 that affords a sealing zone seal.

6 corresponding to the sealing zone 5. Both these sections 2, 6 are preferably of low-expansion heat-resistant glass. Within the envelope I, at or in definite optical relation to the focal point of the reflecting surface 3, is mounted the electrical energy-translation means or light source III, here represented merely by a single linear coil of refractory metal such as tungsten. As shown in Fig. 3, the inner surface of the cover or lens 6 has flutings II for directing and distributing the light from the translation means II) as desired. The inlead connections I2, I2 through the reflector 2 and their vacuum and gas-tight seals may correspond to what is shown in my lastmentioned patent, and the connections I2, I2 are shown as provided with apertured external bracket terminals I3, I3 behind the reflector 2. After the sections 2 and 6 have been sealed together, the envelope I may be evacuated and filled with a suitable gaseous medium (if desired) by means of an exhaust tube I4 at the apex of the reflector 2, after which this tube may be tipped or sealed on as shown.

As shown in Figs. 2 and 3, the rims I and 8 and the sealing zones 5 and 8 of the sections 2 and 6 may correspond essentially to those in my last-mentioned patent: e. g., the annular sealing zones 5 and 9 may have a uniform mating width of about inches. Inside the zone 5, likewise, the rim 4 may be rabbetted on a bevel to a depth of some inch and a bottom width of about the same, and inside the zone 9, the rim 8 may be rabbetted to a similar bottom width, though to a much less depth. To align the section 6 coaxaxially with the section 2 for sealing thereto, these parts are provided with interlocking matched protuberances or keys I5 and depressions or keyways I6. Preferably the keys I5 are of slightly greater height or depth than are their corresponding keyways I6. As indicated in Figs. 1, 2, and 3, there are four keys I5 on the front section 6 and four corresponding keyways I6 in the rear section 2, all spaced 90. To orient the lens features II of the cover 6 relative to the reflector 2 and the translation means III, one projection I5 and its corresponding recess or socket I6 are made larger than the others. As shown, the keys and keyways I5, I6 occupy about half the width of the zones 9, 5 at their outer edges. In practice, the keys I5 may be about 5 inch wide and 5: inch high, with a length of about V inch circumferentially of the zone 9 for all but one of them, which may be about double this length.

In sealing the sections 2 and 6 together, the reflector section 2 is mounted face-up in a rotatable holder (not shown), and the cover section 6 rests thereon by its own weight, being properly aligned and oriented (with the sealing zones 5, ii in registry) by the interfitting and interlocked key means I5, I5. The assembled sections 2, 6 are then rotated while sharp-pointed sealing flames I! (only one of which is indicated in Fig. 1) play on the joint" of the sealing surfaces 5, 9, until the glass at these surfaces becomes fused and unites the parts in a fused glass While this seal is still soft and plastic, air or gas under pressure may be admitted to the envelope I through the exhaust tube It to blow up" or raise the cover 6 slightly (the extent may be determined by suitable stop means, not shown), thus stretching or working the glass of the seal and producing a rounded inner seal boundary I8, Fig. 1, which makes for a strong, strain-free joint-as contrasted with a sharp crevice or corner in the seal, which would make for weakness and easy initial cracking through the joint.

During the formation of the joint as just described, heat therefrom travels inward in the cover rim 8 and into the circumferential wall or flange I, tending to soften it or at least reduce its resistance to stress, so that it does not become strained or internally stressed. At the same time, the wall 1 serves to isolate the flat radiation-transmitting cover portion from the rim 6, so that no dangerous thermal strain or internal stress is set up in this fiat portion. Accordingly, the envelope I formed by the interfusion of the sections 2, 6 is free from strain or stress that would tend to produce cracking. This is in marked contrast with the reverse situation in the case of a mere fiat cover with its margin lapped over the reflector sealing zone 5 and fused directly thereto.

A polarizing layer I9 may be applied to the fiat front face of the cover 6 very easily and conveniently, preferably after the cover 6 has been sealed to the rear section 2. For this purpose, I may use a. commercially available polarizing sheet material consisting of a transparent carrier sheet of plastic having thereon an adherent film of oriented polarizing particles, and preferably provided with a coating of thermo-softening adhesive over its polarized face. The cover 6 being gently heated or warmed, a suitable sheet of this character is laid on its front face with the adhesive next the glass, and is pressed against the glass until firmly bonded thereto all over, as shown in Fig. 1.

If desired, the polarizing film I9 may be on a carrier sheet of glass 26 which may be cemented to the front face of the cover 6 with transparent adhesive 2|, as shown in Fig. 4. In this case, the front face of the cover 6may be very slightly crowned, as shown, to facilitate the flowing and drying of the adhesive.

Alternatively, if preferred, the polarizing film I9 may be laminated between two sheets of plate glass 20, 20, and this secondary cover section may be c'emented to the front face of the cover 6, Fig. 5. In this case, the cover 6 may have an outstandin marginal flange 23 into which the edge of the glass sheets 20, 20 may fit and be cemented. If the sheet 20 remote from the cover 6 is made thin enough (of the order of thousandths or hundredths of an inch), heat strains in it will not undo the polarizin effect of the film I9.

Figs. 6, 'i, and 8 illustrate a modification in which one of the envelope sections has a sealing zone 5 formed by the top of a lateral flange of narrow width and considerable height outstanding therefrom along its periphery, while the outer margin of the other section is substantially plain. In the present instance, the sealing flange 5 projects from the rim 4 of the reflector 2 to a height of about 1*; inch, and has a top width slightly less than this. To provide an external mounting shoulder 24, the plain cover 6 has its margin slightly offset toward the reflector as a short of rim 8, of a width of about inch or more. Aligning and orienting key means similar to those already described (not shown) may be provided on these rims 8 and 4, if any feature of the cover 6 makes orientation desirable.

In sealing the sections 2', 5 to one another, they are rotated together relative to fine, short sealin flames I! (only one of which is indicated in Fig. 8) which play on the joint and very quickly fuse the flange 5 and soften the abutting surface of the cover rim 8 sumciently to unite and seal the parts together; but this is preferably accomplished without melting down the flange 6, which as shown in Fig. 8 retains almost its full height. The cover rim 8 is not appreciably modified by the sealing operation, except in being stuck to the top of the flange 5 to form a, gas and vacuum-tight seal of ample mechanical strength. No light-polarizer is shown in Figs. 6, 7, 8, although one might obviously be applied in the same way as in Fig. 1.

The modification here described in connection with Figs. 6, 7, and 8 has been found especially suitable for relatively small lamps, of some 4 or 5 inches diameter. For ordinary head-lamps of some 7 inches diameter or larger, the construction V described in connection with Figs. 1, 2, and 3 may be preferred as giving greater strength.

It will be understood that the dimensions and materials hereinbefore mentioned are illustrative, and are not to be taken as defining or limiting the invention, since in practice the dimensions may be varied and other materials may be used.

In Figs. 4, 5, 6, 7, and 8, various parts and features are marked with the same reference characters as their homologues in Figs. 1, 2, and 3, as a means of dispensing with repetitive description.

What I claim as new and desire to secure by Letters Patent of the United States is:

Number A projection lamp comprising a glass reflector section and a dish-shaped glass cover section with a planar end wall portion and a circumferential side wall portion fused at its periphery to the periphery of said reflector section and forming an enclosure for a light source, said cover section having a forwardly projecting marginal flange, and a secondary planar cover section carrying a film of light-polarizing material and secured to the said marginal flange in spaced relation to the surface of the end wall portion of said firstunentioned cover section.

DANIEL K. WRIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,252,324 Land Aug. 12, 1941 2,362,172 Swanson Nov. 7, 1944 2,268,670 Ronci Jan. 6, 1942 FOREIGN PATENTS Number 7 Country Date 665,597 German Sept. 29, 1938 

